Save the dates

Generally you send Save the Dates to two groups of people:

1. The most important guests/people you can't imagine your wedding without (immediate family, bridal party, closest friends, etc)

2. Out of town guests that will need to arrange travel/accommodations, so they have plenty of time to do so

I had some extra, which I sent to our vendors!

I think what you're saying is you're having a smaller, intimate ceremony followed by a larger reception. If this is the case, I'd send STD's to everyone. When you send out the invites, I would make 2 different ones and clarify on the reception-only invites something like "reception only, dinner and drinks until 10" at the bottom.

Kind of how on classic invites, the bottom says "reception to follow".

I'm confused about your plan. Is this a tiered event, with different groups of people attending different parts?